Terminal and seal construction for electric lamps and similar devices



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Dec. 26, 195o J. YODER 2,535,773

TERMINAL AND SEAL CONSTRUCTION FOR ELECTRIC LAMPS AND SIMILAR DEVICES Filed April 17, 1943 2 Sheets-Sheet 2 lm/en'toV Joe Yoder, by Q1/m His Aftorney.

Patented Dec. 26, 1950 STAIjEs PATENT OFFICE TERMINAL AND SEAL CONSTRUCTION FOR ELECTRIC LAMPS AND SIMILAR DEVICES Joe Yoder, Cleveland, Ohio, assigner to General Electric Company, a corporation of New York Application April 17, 1943, serial No. 483,470

4 Claims. l

This invention relates to basing land envelope construction for electrical devices, including electric jlamps and discharge devices, and involves novelty in structure as well as in fabrication. The invention' is especially advantageous for electric lamps whose envelopes have tubular necks or end portions, including lamps lf tube form such as ord nary fluorescent lamps of the usual .positive column discharge type-although itis also adaptable to other types of lamps and electric translation devices. In suitable forms olf-embodiment, the invention aiords advantages in maximum utilizat'on'of the tubular envelope wall for useful light output; simplicity and economy of envelope fabrication; ease and cheapnessrin the basing operation; simplic'ty and ruggedness of the base. and ease and cheapness in its manufacture; and economy of material in the construction of .the base. Indeed, the invention even permits of dispensing ent'rely with a base as a separate structure, by incorporating the usual base contact terminals into the envelope construction.

In forms of embodiment of the invention here illustrated and described, a tubular discharge envelope is constructed w'th a reentrant-walled end, embodying an end-piece or wall set back behind the extremityof the tubular wall. In some forms, this set back end portion is shown as a stem flare and inlead seal of the general type now commonly used in fluorescent lamps; while ln other forms, it is shown as an inlead seal disc which isin itself rather like those of certain vacuum-tubes. The set-back end portion is connected to the extremity of the main tubular wall by a reentrant annular or frustro-conical inner wall, which coacts with the end piece to form an external end cavity. l 'I'he preferred method of fabrcation of the reentrant end wall that is hereinafter de scribed is to fuse the tubular wall to the edge of the end-piece and to shift the end-piece further inward into the tube, while the material is soft, thus draw'ng, stretching, and' retroverting the joint and the tubular Wall outside-in into the tube to form the reentrant inner wall. A contactterminal-carrying insulative' base may be cemented over and into the external end cavity, or may even consist essentially of :an insulative thermoplastic filler adherent to the internal cavity wall and to contact-terminal parts or biposts" embedded and anchored directly in the plastic. substantially without direct attachment to the envelope, though connected to the inlead wires. Alternatively, the contact-terminals may be sealed into or through the reentrant end wall of the envelope. and thus anchored or attached 2 directly and more firmly to the latter. When the contact-terminals are thus anchored strongly enough in a suiiiciently rugged end wall, the insulative ller in the end cavity may be omitted, doing away ent rely with any distinct base structure.

Various other features and advantages of the invention will become apparent from the description of species land forms of embodiments, and from the drawings.

In the drawings,

Fig. 1 is a fragmentary long-'tudinal sectional view of a vitreous tubular envelope end and a base therefor conveniently embodying the inven,- tion; and Figs. 2 and 3 are similar views illustrating modifications.

Figs. 4, 5, 6, and 7 are fragmentary longitudinal sectional views illustrating stages in the fabrication of envelope ends such as shown in Figs. 1, 2, and 3 according to the invention.

Figs. 8 and 9 are views similar to Figs. 4 and 7 illustrating another forms of construction and its manufacture.

Figs. 10 and 1l are views similar to Figs. 8 and 9 illustrating a baseless construction, and Fig. 12 is a view similar to F'g. 11 showing a recess of the envelope end filled in with suitable filler material.

As illustrated :fn Fig. 1, the lamp L may be a discharge lamp of tubular form and of positive column low-pressure type, comprising a glass envelope tube I0 with a reentrant-walled end II. The reentrant end II is shown as forming part of a cathode mount that includes a short hollow glass stem and flare I2 terminating in a fused seal I3 through which the current leads I 4, I 4 to the cathode I5 enter the envelope IU. The cathode I5 may consist of the usual coiled coil of tungsten wire coated with activating oxides, such as a mixture including barium and strontium ox'des, and may be supplemented with the usual unactivted anodeis) I6 formed by transverse extensions of lead wire(s) I4. When the device L is a uorescent lamp, its tubular wall I0 is made luminescent under excitation by the radiation due to the electrical d'scharge therein, .as by means of an internal coating of phosphor I1 on said wall. The envelope I 0 may contain a low pressure atmosphere of starting gas, such as argon at a pressure of 2 to 4 mm. of mercury, and also tion fixed in the reentrant envelope wail cavity at ii. auch as thermoplastic or cement (e.g., sealing wax) adherent to the internal wall of the cavity, which it may even fill completely, including the whole interior of the stem i2. Contact` terminals 2i 2i for the filament i5 are embedded and anchored or fixed in the insulative fller 20, in the form of hollow posts which project outward from the base substantially beyond the extremity of the main tube. and into which the current lead wires i4. i4 are threaded and soldered or welded. As shown. the bipost contacts 2i, 2l have enlarged collars or flanges 22, 22 about at midlength, which lie at the surface of the insulating plastic or cement 20 and thus fix the longitudinal positions of the posts relative to the insulation.

It will be appreciated that as the base 20 leaves the luminescent envelope wall IU exposed and unobscured right to the very extremity of the envelope tube, this wall can be fully utilized for useful light output: and when the envelope is rendered luminescent by a phosphor coating or layer at its inside, this layer may usefully extend to the very end of the wall i0. and even inward back on the wall of the reentrant cavity i l. It will he understood that for the usual fluorescent lamp the other end of the lamp is provided with a similar electrode and base structure.

Fig. 2 shows an envelope end portion L essentially the same as in Fig. 1, and in addition shows an exhaust tube 24 opening through the stem seal I3. but itself sealed ou at its end 25. The base 20a differs from the base 20 of Fig. i in comprising a circular disc whose peripheral margin abuts laterally against the extremity of the envelope I where its wall bends inward to the reentrant portion i l together with insulative thermoplastic or cement 2G adherent to the inner surface of the disc, as well as to the internal wall of the end cavity il, and thus securing the disc to the envelope end. As shown, the mid-portion of the disc a is thickened into a protuberance that is circumferentially undercut on a bevel at 21, and the cement 25 interlocks with or behind this undercut. The contact-terminal posts 2i, 2| are fixed in the clisc 20a by having their inner ends riveted over at 28, 28. The disc 20a is shown with a central opening or hole 29 therein to accommodate the sealed end 25 of the exhaust tube 24. The disc 20a may consist of any suitable material, preferably insulative, such as molded plastic, indurated fiber, or glass-or even of metal, if suitable provision is made for insulating the contact terminals `2i, 2i therefrom, or at least from one another.

As regards its base 20h. the construction shown in Fig. 3 differs from that of Fig. 2 in having a central thickening or protuberance formed by means of a separate disc 3D (with undercut outer edge 2lb) which is riveted :and secured to the main base disc by means of the biposts 2i, 2i. As regards the envelope, there is a difference in the conformation of the reentrant end wall IIb. which presents an annular bend 3| where the conicity or flare of the wall increases. The signicance of this will become apparent hereinafter.

In fabricating an envelope end for a fluorescent lamp according to this invention, the first step of the operation may correspond in a broad way to present fluorescent lamp practice. As shown in Fig. 49a cathode mount M such as usually used for fluorescent lamps-comprising as end piece for the envelope a so-called are" il on the stem" part i2 through whose seal I3 the current leads il. it extend to the cathode iB-is about to be sealed into the lower end of an upright envelope tube i0 by means of gas flames from circumjacent burners 32. Usually, envelope tubes for fluorescent lamps are made with their ends reduced in diameter by an inward offset of the edge, and the tube end i0 is so shown at 33 in Fig. 4. Also. the envelope tube I0 is commonly and preferably coated internally with phosphor powder ilbefore the mount M is sealed into it; but to prevent phosphor on the end portion 33 from interfering with the sealing in, this portion 33 is left uncoated, or the coating on it is removed in advance of the sealing in operation. The tube I0 may be held in a vertically shiftable clamp 34. and the mount M may be held or supported by a vertically shiftable hollow metal support 35 which receives the exhaust tube 24 and has a more or less conical head 36 that fits up into the stem i2. The support 35 may be slotted and grooved as shown to accommodate the lead wires i4, I4. In accordance with usual sealing-in practice, the burners 32 may revolve relative to the parts l0. M, 34, 35, or vice versa.. The flames from the burners 32 play on the edge portions of the tube end 33 and of the flare ii to heat and soften them until they coalesce in a fused" seal. However. it will be understood that other means of heating the glass might be employed in forming the seal.

If performed as just r -tliout anything further, the sealin suit after cooling in a tube as illustrated in Fig. 5. whe` exif the flarev ii joins the reduced tubee'dgfpprton- 33 almostat a sharp angle, and the'redil'ti'in. diameter at 33 is retained almost-unmodified; In former practice, this was the caseand'thereducticn at 33 afforded room and even a.`v practicable lip-hold 31 for basing cement to secure to' the envelope end l0 a base comprising a disc about like that in Fig. 3 with a laterally projecting sheetr'netal band or skirt attached to its p'eri'pl ieynot shown.

In accordance with thislinfv'etion the end conformaticn a3 that is sho.- Q iSmOdifieu. In part, at least, this may ected'gby a meas-- ure that also assists in uni i, gfthe hot edges of the parts il, 33: namely, byfdirect'positive pressure on these softened and morego'rless coalescent edges. by means of a metal molding head 38 on a sleeve 39 shown in Fig. 4 as telescoped around the support 35. This head 38.is moved up against the soft parts to nally seal them; together (if this is required), and to round'and true up the corner formed by their union. The-effect of this is to more or less obliterate the shoulder or lip 3l, as shown in Fig. 5, besidesregularizing the tube end conformation and shifting the whole mount M further inward in the axial direction into the tube i0.

The inward displacement ofthe stem and flare ii, I2 by action of the head'38 on the seal at 33 may be supplemented or substituted by an axial inward shift otherwise eiected; If resorted to as a measure additional to the pressure cf the head 38 on the seal 33, this may be done either during such pressure or afterward. In either case, the flare il (and the whole mount M) is shifted inward into the tube end portion I0, while the material is heated and soft, by force exerted more directly on the mount or flare, thus drawing and retroverting the edge or marginal perton of the envelope wall at 33 reentrantly outside-in and stretching or pulling it straight (more v o r less perfectly) into an inturned frusto-conical mation such4 1 .annuius :wat .tnefbasef of the-nare n 'annost corresponding in corlicity to the flare itself-all as shown in Fig. 3 or Fig. 6, where the slight angle or diii'erence .of conicity of the reentrant wall at 3| corresponds to the fused seal between the original are II and the inturned tube edge portion 33h. This is preferably done while the portions of tube I and flare I I'are still soft from the heat used in sealing them together as above described in connection with Fig. 4,' rather than by reheating them. In this operation, the original offset at 33 in Fig. 4 is faired away and virtually or nearly abolished If the material of the tube edge portion and of the flare is suitably soft over suillciently wide zones, and the mount M is shifted inward far enough, the angle at 3| may be fiattened out until all trace of it virtually disappears, resulting in a reentrant end wall of substantially uniform conicity, as shown in Figs. 1, 2, and 7. Indeed, part of the cylindrical tube wall shown in Figs. 4 and 5 will generally beN turned outsidein and thus incorporated into the reentrant end wall. The vaxial inward shift of the mount M and flare II may be produced by pushing upward on them by means of the support 35 while the envelope l0 is held fixed by means of the clamp 34, or by pushing downward on the envelope I0 by means of the clamp 34, or by a combination of 'such movements, or in any other suitable way.

It will be seen that the turning outside-in of the tube wall at 33 (and above) as has been described not only improves the conformation of 6 weight of the subjacent tube end, which ultimately fuses through below the seal and drops off. Thereupon the support 35e may be raised higher to shift the disc IIc and the whole mount Mc further inward 'into the tube I0, thus pulling, stretching, and turning or retroverting the fused seal (and even the soft wall of the tube I0) outside-in into the end of the tube I il as shown at 33e in Fig. 9. The reentrant-ended tube may then be',

based in any of the ways illustrated in Figs. 1, 2, and 3, or in any other suitable manner.

Figs. 10 and 11 illustrate a variant vof the method and construction shown in Figs. 8 and 9 whose distinctive feature is that instead of having through" leadwires I4, I4 sealed through the disc end piece I Id and afterward connected to contact terminal pins of a distinct or separate base structure. as in Figs. 1-3, the contact terminal pins 2 ld, 2 Id are themselves sealed directly through the disc IId at4ld, .40d and carry short internal leadwires I 4d, I4d between which the cathode coil I5 is connected. In other respects, this construction and its fabrication may correspond to what has already been described in connection with Figs. 8 and 9, including the pulling.

' stretching, and turning in of the fused seal at 33d and the wall of the tube I0. ubase" Thus the lamp is essentially merged in the lamp envelope end construction. and special basing operations the tube end and gets rid of the unsightly reduction in diameter at 33 without necessity for a s'kirted base to hide it, but also results in having 'the luminescent cylindrical tube wall I0 extend right to the very end of the tube, with the resultant advantage already mentioned in connection with Fig. 1. Even if the envelope tube end I0 lacked the end reduction 33 or any corresponding feature, the retroversion outside-in of part of the cylindrical tube wall would produce a similar advantage in respect c-f the zone of fusion produced in sealing the flare I I to the tube-end edge.

Figs. 8 and 9 illustrate the application of the invention to a mount Mc in which the stem and flare type end piece of Figs. 1-7 are replaced by a simple glass disc end piece llc'which the leadwires I4, I 4-penetrate through bead-like internal and external seal protuberances 40, 4U, and through which the axial exhaust tube 24 opens centrally between the seals 40, 4I). Such a mount may be fabricated by the glass-working methods commonly used in fabricating the multi-lead ends of vacuum tubes of various kinds, with the slight modification naturally indicated by the fact that only two leads I4, I4 are sealed through the disc IIc. The mount Mc is shown in Fig. 8-as supported by a vertically movable hollow metal support e that receives the exhaust tube 24 and has an enlarged flat head 36e with, flared apertures for the lead-wires I4, I4 and the seals 40, 40. Instead of having reduced ends as at 33 in Fig. 4. the envelope tube I0c may originally be of uniform bore: and instead of the method usually employed for sealing in fluorescent lamp mounts M as illustrated in Fig. 4, the mount Mc may be sealed in according to usual incandescent lamp practice: that is to say. the upright tube portion I0 is placed around the mount disc II c with the latter some distance (e. g., some 1 to 1% inches) above the open lower tube end, and the tube Ic is then heated by flames from the circumjacent burners 32 until it draws and necks in into a fused seal with the disc edge by the are dispensed with. 'I'he pins 2 Id. 2Id are firmly fixed in the glass of the end construction, which is very strong and rigid. As shown in Fig. 12, nevertheless, the cavity of the reentrant lamp end may if desired be filled in around the pins 2Id. 2id and the exhaust tube seal 25d with an insulative ller 20d of cement` sealing-wax, or other thermoplastic-like Bakelite, for instancevery much as in Fig. 1, thus fortifying the anchorage of the pins, and protecting the seal 25d and the reentrant tube end I Id from accidental damage.

It will readilv be appreciated that the constructions illustrated in Figs. 9. 11, and 12 not only a1- low of rendering the tube wall luminous with phosphor I 1 right up to the very end IId and even on the main central area of the latter, but also allow of placing the cathode I5 as close as possible to the very end of the tube wallA so that all the phosphor coating .shall be effectively excited bv the electric discharge in the tube.

In Figs. 2, 3, and 5 to l2, various parts and features are marked with the same reference characters as are applied to corresponding parts in the earlier figures. in order to dispense with repetitive description, a distinctive letter being addsd where such distinction appears useful.

Certain features disclosed herein relating to the methods of fabricating tubular envelopes generally are being claimed in my cooending divsional application Serial No. 690,661, filed August l5, 1946, and which is assigned to the assignee of the present application.

What I claim as new and desire to secure by Letters Patent of the United States is:

l. In a fluorescent discharge device, the combination of a tubular envelope portion having a reentrantlv inturned marginal portion, a. cathode mount in the envelope including an end piece itself sealed to said inturned marginal portion of the envelope wall within the reentrant region and forming with said marginal portion a reentrant end wall for the envelope closing the end thereof, a coating of fluorescent material on *he inner wall of said envelope. said coating extending at least right to the reentrant inofv the seal in said reentrant end wall between the end piece and the in-turned marginal portion of the envelope wall, and terminal means on said envelope at the end thereof and leaving the envelope wall exposed right to the said reentrant irl-turn therein, said terminal means comprising contact-terminal posts for the cathode of the mount projecting endwise from the end oiLthe envelope substantially beyond the said in-turn. e

2. The invention as set forth in claim l wherein said contact-terminal posts are sealed and anchored in said end piece.

3. -In a iluorescent discharge device, the combination of a tubular envelope portion having a reentrantly irl-,turned marginal portion, a cathode mount in the envelope including an end piece itself sealed to said inturned marginal portion o! the envelope wall within the reentrant 2o region toform a rounded reentrant union surface near the lenvelope end and forming with said marginal portion a reentrant end wall for the envelope closing the end thereof, a coating of fluorescent material on the inner wall of said envelope, said coating extending at least right to the reentrant in-turn inthe envelope `wall but terminating short of the seal. in said reentrant end wall between the end piece and the in-turned marginal portion of the envelope wail, and a base secured to the 'emi of said enveiope and leaving the envelope wall exposed 8 right to the said in`turn therein, said base having contact-terminal posts for the cathode foi' the mount projecting "endwise from the end of the envelope substantially beyond the saidinturn 4. .The combination with an envelope having a reentrant-walled end dening a reentrant cav.-

ity, of a base disc at the envelope end having an undercut protuberance on its inner side, and cement `fast in said cavity interlocked with the undercut of saidv disc protuberance, and thus securing the disc to the envelope.

JOE YODER.

RnFnRnNcEs crrnn UNITED STATES PATENTS Number Name Date 514,495 Pilkington Feb. 13, 1894 1,674,182 Siegheim June 19, 1928 1,824,452 Wamser Sept. 22, 1931 2,109,274 Niclassen Feb. 22. 1938 2,267,118 Marden Dec. 23, 1941 2,279,907 Atchley Apr. 14. 1942 2,322,224 Cox June 22, 1943 2,334,631 Johnson Nov. 16, 1943 FOREIGN PATENTS Number Country Date 527.940 Great Britain Cet. 18. 1940 

